Method and structure for reinforcing tunnels



May 5,- 1970 3,509,725

METHOD AND STRUCTURE FOR REINFORCING TUNNELS Filed Aug. 12, 1968 H. SCHNAB'EL, JR

2 Sheets-Sheet 1 T INV ENTOR HARRY SCHNABEL, JR.

May 5, 1970 H. SCHNABEL, JR

METHOD AND STRUCTURE FOR REINFORCING TUNNELS 2 Sheets-Sheet 2 Filed Aug. 12, 1968 I NVENTOR HARRY SCHNABEL, JR.

United States Patent 3,509,725 METHOD AND STRUCTURE FOR REINFORCING TUNNELS- Harry Schnabel, Jr., 7010 Longwood Drive, Bethesda, Md. 20034 Filed Aug. 12, 1968, Ser. No. 751,770 Int. Cl. E21d; E01g /16 US. Cl. 61-45 5 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention The present invention relates to subterranean tunnels and more particularly to support structure for such tunnels.

Description of the prior art Conventional practices for lining and supporting tunnels have in the past included the use of the rigid and massive cylindrical liners. An example of this type construction employs spaced H-beam rings with wood lagging extending therebetween. Such liners are very expensive and very heavy.

In an effort to reduce weight and cost, lighter liners backfilled with earth or grout were employed. For example, both circular and noncircular liners of steel plate backfilled with concrete grout were utilized. Some improvement was realized but difficulty was encountered in obtaining a tightly packed, uniformly distributed backfill. The grout tends to slump along its angle of repose from the top center of each liner section both laterally and longitudinally. Thus, much space above the liner is left unfilled particularly toward the ends of each liner section. Without proper backfill, the natural compressive strength of the earth around the liner is not used to advantage. Thus, the inherent strength and mass of the liner must be increased accordingly.

In summary, tunnel construction using liners which are not adequately and compactly backfilled present two primary disadvantages irrespective of whether the liner is circular or of other cross-sectional configuration. The structural components of the liner must be of a very heavy gage; and the probability of settlement and res-ultant structural damage is great.

SUMMARY OF THE INVENTION Accordingly, it is a major objective of the instant invention to provide a method and structure for reinforcing tunnels wherein proper backfilling of a liner is facilitated, irrespective of the shape of the liner, thereby utilizing the compressive strength of the surrounding earth to maximum advantage.

Another very important object of the invention is to provide such a method and structure wherein a specially configured inflatable bladder is disposed between the liner and the roof of the tunnel and filled with grout to extend the bladder surfaces into mating pressure engagement with both the liner and the roof.

The above and other objects of the invention can be accomplished by utilizing the method and structure of ice the invention. Broadly stated, a support structure is provided for a subterranean tunnel having a curved earthen roof, which structure includes a primary liner having a curved outer wall generally conforming in configuration to the earthen roof and flexible bladder means having an outer convex surface and an inner concave surface generally conforming in configuration to the tunnel roof and the outer liner wall respectively. The liner and bladder means are inserted into the tunnel with the outer liner wall conforming to and spaced from the tunnel roof and with the bladder means mounted therebetween, said convex and concave bladder surfaces conforming to said roof and said wall respectively. The bladder means is filled with hardenable fluid grout to extend said outer convex surface and said inner concave surface into mating pressure engagement substantially through out each of said surfaces with the tunnel roof and the liner wall respectively. The grout is then permitted to harden to retain the surrounding earth in substantially uniform compression and to distribute substantially uniformly over the liner wall the forces exerted thereon by the surrounding earth.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view of a subterranean tunnel reinforced in accordance with the present invention;

FIG. 2 is a cross-sectional view taken substantially along line 22 of FIG. 1;

FIG. 3 is a cross-sectional view of a modified form of support structure which embodies the concepts and principles ofthe invention;

FIG. 4 is an isometric view, to a reduced scale, of the bladder means of the support structure of FIGS. 1 and 2; and

FIG. 5 is an isometric view, to a reduced scale, of the bladder means of the support structure of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A support structure according to the present invention is illustrated in FIGS. 1 and 2 of the drawings and is broadly designated therein by the numeral 10. Structure 10 is utilized for supporting a subterranean tunnel 12 having an earthen wall 14. Tunnel wall 14 extends continuously around the periphery of tunnel 12 and includes a generally concave roof portion 16, a generally concave floor portion 18 oppositely spaced from roof portion 16, and a pair of opposed, spaced side portions 20 and 22 which extend between portions 16 and 18 and are continuous therewith.

Structure 10 includes an elongated, substantially tubelike, primary liner 24 which has an oval transverse crosssectional configuration greater in height than in width. The liner 24 is provided with a transversely arcuate upper wall segment 26 and a transversely arcuate lower wall segment 28 vertically spaced therefrom. Wall segments 26 and 28 are preferably constructed of steel or the like and are disposed in opposed relationship to present respective oppositely facing, convex outer wall surfaces 30 and 32. Outer surface 30 of wall segment 26 conforms substantially in configuration to roof portion 16 while outer surface 32 of wall segment 28 conforms substantially in shape to floor portion 18. Surface 30 conforms to and is spaced from roof portion 16 to present a transversely arcuate space portion 34 therebetween. Likewise, surface 32 conforms to and is spaced from floor portion 18 to present transversely arcuate space portion 36 therebetween.

A respective longitudinally extending, downwardly opening, channel shaped beam element 38 is secured by welding or the like to each downwardly extending leg 40 of segment 26 by a plurality of gussets 42. Similarly, a respective, longitudinally extending, upwardly opening channel shaped beam element 44 is secured to each upwardly extending leg 46 of segment 28 by a plurality of gussets 48. Each beam element 38 is vertically aligned with a corresponding beam element 44 as shown in FIG. 2.

A side segment 50 extends longitudinally of liner 24 and vertically between each element 38 and its corresponding element 44. Each segment 50 is shown as comprising a plurality of horizontally extending, vertically stacked, wooden slats 52 held in place by a plurality of vertically extending straps 54. Alternatively each side segment 50 could be a metal plate welded directly between a leg 40 and its corresponding leg 46. Each of the segments 26 and 28 are provided with an opening 56 therethrough for a purpose to be explained hereinbelow.

A transversely arcuate, longitudinally extending flexiblebladder 58 is disposed within space portion 34 While a similar bladder 60 is disposed within space portion 36. The bladders 58 and 60 are each inflatable and operable to contain and substantially confine a quantity of initially fiuid grout material 62 which is hardenable to form a rigid, dimensionally stable solid mass. Usually the grout material would be concrete. In this connection, the bladders '8 and 60 are constructed of a flexible material which substantially confines the grout. Preferably, the flexible material comprises a slightly porous fabric such as cloth. The size of the openings in the porous fabric are such as to substantially prevent escape of the solid materials in the grout, but to permit the escape of airand some of the liquid in the grout. However, other flexible materials including rubber or a synthetic resin such as polyethylene, which substantially confines the fluid grout also could be utilized. In some instances it is not necessary that the flexible material be porous. However if desired, the polyethylene or similar material may be perforated to provide the degree of porosity described hereinbefore. A porous material is preferred because it enables the grout to become harder and to solidify more quickly due to the escape of liquid to the surrounding soil. It also precludes formation of air pockets within the bladder.

Bladder 58 has an outer convex surface 64 and an inner concave surface 66. The surfaces 64 and 66 are opposed and the former conforms substantially in configuration to roof portion 16 while the latter conforms substantially in configuration to the outer surface 30 of the upper liner wall. Bladder 60 has similar outer convex and inner concave surfaces 68 and 70 which conform substantially in configuration to floor portion 18 and liner wall surface 32 respectively. Thus, the convex bladder surfaces 64 and 68 are disposed in complementally mating relationship to roof portion 16 and floor portion 18 respectively; and the concave bladders surfaces 66 and 70 are disposed in complementally mating relationship to liner wall surfaces 30 and 32 respectively.

The bladders 58 and 60 are each provided with a filler tube 72 which extends through a corresponding opening 56 in the liner wall. Thus, the tubes 72 may be connected with a source (not shown) of pressurized fluid grout to fill the bladders 58 and 60 which are thus extended by the grout to completely occupy their respective space portions 34 and 36 to bear in pressure engagement against respective roof and floor portions 16 and 18 and respective liner wall surfaces 30 and 32. Such pres-sure engagement occurs substantially throughout the areas of the outer convex surfaces '64 and 68 and the inner concave surfaces 66 and 70. The grout filled bladders thereby place the surrounding earth 74 behind the floor and roof portions 16 and 18 in substantially uniform compression and distributes substantially uniformly over the liner walls 30 and 32 the forces exerted thereon by the surrounding earth. The grout is then permitted to harden in the usual manner to retain the bladders in the thus described relationship to the liner and tunnel wall.

The forces exerted by the earth on the vertical portions 50 are not substantial and therefore portions 50 may be backfilled with earth as illustrated in FIG. 2 at 76.

Support structure comprising a modified embodiment of the invention is illustrated in FIG. 3 and is broadly designated by the numeral 110. In this embodiment, tun- 'nel 112; tunnel wall 114; roof portion 116 and floor portion 118; liner 124; liner segments 126, 128, and 150; liner walls surfaces and 132; space portions 134 and 136; beams 138 and 144; liner legs and 146; gussets 142 and 148; slats 152; straps 154; and openings 56 are substantially identical to the corresponding components of the embodiment of FIGS. 1 and 2 which have similar numbering in the unit rather than the hundred series. Thus, the detailed description of these components will not be repeated.

In the embodiment of FIG. 3, the segments are not backfilled with earth and the portions 120 and 122 of tunnel wall 114 are spaced horizontally from corresponding segments 150 to present respective space portions 158 therebetween. The space portions 158 are horizontally spaced apart and extend vertically between space portions 134 and 126 on opposite sides of liner 124. The portions 158 are continuous with portions 134 and 136 to present a substantially oval ring shaped space 160 which completely surrounds linear 124.

An elongated, flexible, bladder 162 substantially oval in cross section, is disposed within space 160. Bladder 162 is operable to contain and substantially confine a quantity of grout 164 which is hardenable to form a rigid, dimensionally stable solid mass. In this connection, bladder 162 may be constructed of any of the same materials described above for bladders S8 and 60.

Bladder 162 has upper and lower, convex outer surfaces 166 and 168 respectively, and upper and lower, concave inner surfaces 170 and 172 respectively. Convex surfaces 166 and 168 conform substantially in configuration to roof and floor portions 116 and 118 respectively and are disposed in spaced relationship thereto. Likewise, concave surfaces 170 and 172 conform substantially in configuration to liner wall surfaces 130 and 132 respectively and are disposed in complementally mating relationship thereto. A pair of spaced outer side surfaces 174 extend vertically on opposite sides of liner 124 to interconnect surfaces 166 and 168. Likewise a pair of spaced inner side surfaces 176 interconnect surfaces 170 and 172. Thus, bladder 162 extends continuously around liner 124.

Bladder 162 is provided with a pair of filler tubes 178 which extend through corresponding openings 156 in the liner wall. Thus, the tubes 178 may be connected with a source (not shown) of pressurized fluid grout to fill bladder 162 which is thus extended by the grout to completely occupy space 160 and to bear in pressure engagement against roof portion 116 and floor portion 118 and liner wall surfaces 130 and 132. Such pressure engagement occurs substantially throughout the areas of the outer convex surfaces 166 and 168 and the inner concave surfaces 170 and 172. The grout filled bladder thereby places the surrounding earth 180 behind roof and floor portions 116 and 118 in substantially uniform compression and distributes substantially uniformly over the liner walls 130 and 132 the forces exterted thereon by the surrounding earth.

The preferred embodiments of the invention having been described in detail, it will be apparent that various modifications may occur to those skilled in the art.

I claim:

1. Support structure for a subterranean tunnel having a curved, earthen roof said structure comprising:

a primary liner having opposed side walls and a curved upper wall conforming substantially in configuration to said roof, said liner being positioned in the 4. Structure as set forth in claim 2 wherein said tunnel with said upper wall disposed in spaced relabladder is constructed of a synthetic resin. tion to said roof presenting a curved space therebe- 5. Structure as set forth in claim 1 wherein said bladtween; and der is constructed of a synthetic resin.

a flexible arch-shaped bladder positioned in said space 5 R f Ct d and having an outer convex surface and an inner corie erences e cave surface conforming in configuration to said roof UNITED STATES PATENTS and said upper wall respectively, said bladder termi- 3,277,219 10/1966 Turner X nating downwardly With. closed lOWBI edges extending 3 342 033 9 19 7 Crouch et 1 52 2 X ng e pp sed Side a s of Sa d prim ry e 10 3 345 24 10 19 7 Turzino 52 .1 9 X said bladder being filled with grout which extends said 3,351,953 19 7 Shields 52.4 9 X outer convex surface and said inner concave sur- 3,357142 12/1967 Fun-er et aL 5 2 face into mating pressure engagement substantially 3,389,510 6/1968 Stock 52 thIOUghOllt each of said surfaces With said IOOf and 3 39 545 196 Lamberton 1 45 X said upper wall respectively to place the surrounding 15 earth in substantially uniform compression and to FOREIGN PATENTS distribute substantially uniformly over said upper 1,129,289 9/ 1956 France. wall the forces exerted thereon by the earth. 945, 7/ 1956 G rmany- 2. Structure as set forth in claim 1 wherein, said bladder is constructed of a slightly porous fabric. DENNIS TAYLOR Pnmary Exammer 3. Structure as set forth in claim 2 wherein said bladder US. Cl. X.R.

is constructed of cloth. 61-85 

